Over the years, a variety of transmissions have been developed to transfer a driving force from a rotational drive arrangement to a rotationally driven load. While these pre-existing transmissions have been generally adequate for their intended purposes, they have not been satisfactory in all respects.
In many, the drive path from the driving device to the load is physically interrupted during a change from one ratio to another, which can waste energy both from the point of view of rotational energy output by the drive device during the interruption which is not applied to any load, as well as the energy expended to terminate the interruption, for example through heat generated and lost in a friction clutch used to effect and terminate the interruption in the drive path.
A further consideration is that the transition from one drive ratio to another is frequently not very smooth, and can involve inefficiency as a result of the fact that a continuous drive force is not applied to the load and/or a continuous resistance is not applied to the drive device during a transition from one ratio to another.
Some of these problems have been avoided by continuously variable transmissions, for example of the type in which two oppositely oriented conical members rotate about parallel axes, and a drive belt engages each and can move axially to vary the ratio. However, continuously variable transmissions of this type have not proven entirely satisfactory in practice, as evidenced by the fact that the majority of vehicles presently being sold do not include transmissions of this type.
It is therefore an object of the present invention to provide an improved transmission which avoids problems of the type discussed above, in particular by providing a continuous driving force to a load and a continuous resistance to a driving device while changing from one drive ratio to another drive ratio, and which is designed to experience minimal power loss during the transition from one such ratio to another.